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Kioumourtzoglou D, Black HL, Al Tobi M, Livingstone R, Petrie JR, Boyle JG, Gould GW, Bryant NJ. Phosphorylation of Syntaxin 4 by the Insulin Receptor Drives Exocytic SNARE Complex Formation to Deliver GLUT4 to the Cell Surface. Biomolecules 2023; 13:1738. [PMID: 38136609 PMCID: PMC10741561 DOI: 10.3390/biom13121738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/24/2023] [Accepted: 11/29/2023] [Indexed: 12/24/2023] Open
Abstract
A major consequence of insulin binding its receptor on fat and muscle cells is the stimulation of glucose transport into these tissues. This is achieved through an increase in the exocytic trafficking rate of the facilitative glucose transporter GLUT4 from intracellular stores to the cell surface. Delivery of GLUT4 to the cell surface requires the formation of functional SNARE complexes containing Syntaxin 4, SNAP23, and VAMP2. Insulin stimulates the formation of these complexes and concomitantly causes phosphorylation of Syntaxin 4. Here, we use a combination of biochemistry and cell biological approaches to provide a mechanistic link between these observations. We present data to support the hypothesis that Tyr-115 and Tyr-251 of Syntaxin 4 are direct substrates of activated insulin receptors, and that these residues modulate the protein's conformation and thus regulate the rate at which Syntaxin 4 forms SNARE complexes that deliver GLUT4 to the cell surface. This report provides molecular details on how the cell regulates SNARE-mediated membrane traffic in response to an external stimulus.
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Affiliation(s)
| | - Hannah L. Black
- Department of Biology, University of York, Heslington YO10 5DD, UK; (D.K.)
| | - Mohammed Al Tobi
- Institute of Molecular Cell and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (M.A.T.)
| | - Rachel Livingstone
- Institute of Molecular Cell and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (M.A.T.)
| | - John R. Petrie
- Institute of Cardiovascular and Medical Sciences, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - James G. Boyle
- School of Medicine, Dentistry & Nursing, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK;
| | - Gwyn W. Gould
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 ORE, UK
| | - Nia J. Bryant
- Department of Biology, University of York, Heslington YO10 5DD, UK; (D.K.)
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2
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Stepien KP, Xu J, Zhang X, Bai XC, Rizo J. SNARE assembly enlightened by cryo-EM structures of a synaptobrevin-Munc18-1-syntaxin-1 complex. SCIENCE ADVANCES 2022; 8:eabo5272. [PMID: 35731863 PMCID: PMC9216511 DOI: 10.1126/sciadv.abo5272] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 04/18/2022] [Indexed: 05/16/2023]
Abstract
Munc18-1 forms a template to organize assembly of the neuronal SNARE complex that triggers neurotransmitter release, binding first to a closed conformation of syntaxin-1 where its amino-terminal region interacts with the SNARE motif, and later binding to synaptobrevin. However, the mechanism of SNARE complex assembly remains unclear. Here, we report two cryo-EM structures of Munc18-1 bound to cross-linked syntaxin-1 and synaptobrevin. The structures allow visualization of how syntaxin-1 opens and reveal how part of the syntaxin-1 amino-terminal region can help nucleate interactions between the amino termini of the syntaxin-1 and synaptobrevin SNARE motifs, while their carboxyl termini bind to distal sites of Munc18-1. These observations, together with mutagenesis, SNARE complex assembly experiments, and fusion assays with reconstituted proteoliposomes, support a model whereby these interactions are critical to initiate SNARE complex assembly and multiple energy barriers enable diverse mechanisms for exquisite regulation of neurotransmitter release.
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Affiliation(s)
- Karolina P. Stepien
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Junjie Xu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xuewu Zhang
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiao-Chen Bai
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Hwang J, Thurmond DC. Exocytosis Proteins: Typical and Atypical Mechanisms of Action in Skeletal Muscle. Front Endocrinol (Lausanne) 2022; 13:915509. [PMID: 35774142 PMCID: PMC9238359 DOI: 10.3389/fendo.2022.915509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is of fundamental importance to prevent postprandial hyperglycemia, and long-term deficits in insulin-stimulated glucose uptake underlie insulin resistance and type 2 diabetes. Skeletal muscle is responsible for ~80% of the peripheral glucose uptake from circulation via the insulin-responsive glucose transporter GLUT4. GLUT4 is mainly sequestered in intracellular GLUT4 storage vesicles in the basal state. In response to insulin, the GLUT4 storage vesicles rapidly translocate to the plasma membrane, where they undergo vesicle docking, priming, and fusion via the high-affinity interactions among the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) exocytosis proteins and their regulators. Numerous studies have elucidated that GLUT4 translocation is defective in insulin resistance and type 2 diabetes. Emerging evidence also links defects in several SNAREs and SNARE regulatory proteins to insulin resistance and type 2 diabetes in rodents and humans. Therefore, we highlight the latest research on the role of SNAREs and their regulatory proteins in insulin-stimulated GLUT4 translocation in skeletal muscle. Subsequently, we discuss the novel emerging role of SNARE proteins as interaction partners in pathways not typically thought to involve SNAREs and how these atypical functions reveal novel therapeutic targets for combating peripheral insulin resistance and diabetes.
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Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute at City of Hope, Duarte, CA, United States
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Black HL, Livingstone R, Mastick CC, Al Tobi M, Taylor H, Geiser A, Stirrat L, Kioumourtzoglou D, Petrie JR, Boyle JG, Bryant NJ, Gould GW. Knockout of Syntaxin-4 in 3T3-L1 adipocytes reveals new insight into GLUT4 trafficking and adiponectin secretion. J Cell Sci 2021; 135:273617. [PMID: 34859814 PMCID: PMC8767277 DOI: 10.1242/jcs.258375] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 11/18/2021] [Indexed: 11/20/2022] Open
Abstract
Adipocytes are key to metabolic regulation, exhibiting insulin-stimulated glucose transport that is underpinned by the insulin-stimulated delivery of glucose transporter type 4 (SLC2A4, also known and hereafter referred to as GLUT4)-containing vesicles to the plasma membrane where they dock and fuse, and increase cell surface GLUT4 levels. Adipocytokines, such as adiponectin, are secreted via a similar mechanism. We used genome editing to knock out syntaxin-4, a protein reported to mediate fusion between GLUT4-containing vesicles and the plasma membrane in 3T3-L1 adipocytes. Syntaxin-4 knockout reduced insulin-stimulated glucose transport and adiponectin secretion by ∼50% and reduced GLUT4 levels. Ectopic expression of haemagglutinin (HA)-tagged GLUT4 conjugated to GFP showed that syntaxin-4-knockout cells retain significant GLUT4 translocation capacity, demonstrating that syntaxin-4 is dispensable for insulin-stimulated GLUT4 translocation. Analysis of recycling kinetics revealed only a modest reduction in the exocytic rate of GLUT4 in knockout cells, and little effect on endocytosis. These analyses demonstrate that syntaxin-4 is not always rate limiting for GLUT4 delivery to the cell surface. In sum, we show that syntaxin-4 knockout results in reduced insulin-stimulated glucose transport, depletion of cellular GLUT4 levels and inhibition of adiponectin secretion but has only modest effects on the translocation capacity of the cells. This article has an associated First Person interview with Hannah L. Black and Rachel Livingstone, joint first authors of the paper. Summary: Syntaxin-4 knockout reduces insulin-stimulated glucose transport, depletes levels of cellular GLUT4 and inhibits secretion of adiponectin but only modestly affects the translocation capacity of the cells.
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Affiliation(s)
- Hannah L Black
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Rachel Livingstone
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Cynthia C Mastick
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.,Department of Biology, University of Nevada Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
| | - Mohammed Al Tobi
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Holly Taylor
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Angéline Geiser
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Laura Stirrat
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Dimitrios Kioumourtzoglou
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - John R Petrie
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK
| | - James G Boyle
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK.,School of Medicine, Dentistry and Nursing, University of Glasgow. Glasgow G12 8QQ, UK
| | - Nia J Bryant
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Gwyn W Gould
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
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Zhang Y, He L, Chen X, Shentu P, Xu Y, Jiao J. Omega-3 polyunsaturated fatty acids promote SNAREs mediated GLUT4 vesicle docking and fusion. J Nutr Biochem 2021; 101:108912. [PMID: 34801692 DOI: 10.1016/j.jnutbio.2021.108912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/24/2021] [Accepted: 10/08/2021] [Indexed: 11/27/2022]
Abstract
Glucose homeostasis imbalance and insulin resistance (IR) are major contributors to the incidence of type 2 diabetes. Omega-3 polyunsaturated fatty acids (PUFAs) are key ingredients for maintaining cellular functions and improving insulin sensitivity. However, how omega-3 PUFAs modulate the dynamic process of glucose transport at the cellular level remains unclear. Here we unraveled eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may regulate the glucose transporter 4 (GLUT4) vesicle trafficking in both normal and IR adipocytes. Both omega-3 PUFAs significantly increase glucose consumption within a range of 10-32% in the basal state. Furthermore, both EPA (200 μM) and DHA (100 μM) may significantly promote the serine/threonine protein kinase (Akt) phosphorylation by 70% and 40% in the physiological state of adipocytes, respectively. Both omega-3 PUFAs significantly advanced the Akt phosphorylation in a dose-dependent way and showed a ∼2-fold increase at the dose of 200 μM in the IR pathological state. However, they could not up-regulate the expression of GLUT4 and insulin-regulated aminopeptidase protein. We further revealed that both omega-3 PUFAs dynamically promote insulin-stimulated GLUT4 vesicle translocation and soluble N-ethylmaleimide-sensitive factor attachment protein receptor mediated vesicle docking and fusion to the plasma membrane via specifically modulating the expression of vesicle-associated membrane protein 2. Understanding the mechanisms by which omega-3 PUFAs modulate cellular metabolism and IR in peripheral tissues may provide novel insights into the potential impact of omega-3 PUFAs on the metabolic function and the management of IR.
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Affiliation(s)
- Yu Zhang
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lilin He
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiaoqian Chen
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ping Shentu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yingke Xu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China; Department of Endocrinology, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
| | - Jingjing Jiao
- Department of Nutrition, School of Public Health, Department of Clinical Nutrition, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
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Maier G, Delezie J, Westermark PO, Santos G, Ritz D, Handschin C. Transcriptomic, proteomic and phosphoproteomic underpinnings of daily exercise performance and zeitgeber activity of training in mouse muscle. J Physiol 2021; 600:769-796. [PMID: 34142717 PMCID: PMC9290843 DOI: 10.1113/jp281535] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 06/11/2021] [Indexed: 12/14/2022] Open
Abstract
Key points Maximal endurance performance is greater in the early daytime. Timed exercise differentially alters the muscle transcriptome and (phospho)‐proteome. Early daytime exercise triggers energy provisioning and tissue regeneration. Early night‐time exercise activates stress‐related and catabolic pathways. Scheduled training has limited effects on the muscle and liver circadian clocks.
Abstract Timed physical activity might potentiate the health benefits of training. The underlying signalling events triggered by exercise at different times of day are, however, poorly understood. Here, we found that time‐dependent variations in maximal treadmill exercise capacity of naïve mice were associated with energy stores, mostly hepatic glycogen levels. Importantly, running at different times of day resulted in a vastly different activation of signalling pathways, e.g. related to stress response, vesicular trafficking, repair and regeneration. Second, voluntary wheel running at the opposite phase of the dark, feeding period surprisingly revealed a minimal zeitgeber (i.e. phase‐shifting) effect of training on the muscle clock. This integrated study provides important insights into the circadian regulation of endurance performance and the control of the circadian clock by exercise. In future studies, these results could contribute to better understanding circadian aspects of training design in athletes and the application of chrono‐exercise‐based interventions in patients.
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Affiliation(s)
- Geraldine Maier
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Julien Delezie
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Pål O Westermark
- Leibniz-Institut für Nutztierbiologie, Institut für Genetik und Biometrie, Wilhelm-Stahl-Allee 2, Dummerstorf, D-18196, Germany
| | - Gesa Santos
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Danilo Ritz
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Christoph Handschin
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
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Patel BM, Goyal RK. Liver and insulin resistance: New wine in old bottle!!! Eur J Pharmacol 2019; 862:172657. [DOI: 10.1016/j.ejphar.2019.172657] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 09/02/2019] [Accepted: 09/05/2019] [Indexed: 12/20/2022]
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Bowman PRT, Smith GL, Gould GW. GLUT4 expression and glucose transport in human induced pluripotent stem cell-derived cardiomyocytes. PLoS One 2019; 14:e0217885. [PMID: 31344028 PMCID: PMC6657831 DOI: 10.1371/journal.pone.0217885] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 07/15/2019] [Indexed: 01/07/2023] Open
Abstract
Induced pluripotent stem cell derived cardiomyocytes (iPSC-CM) have the potential to transform regenerative cardiac medicine and the modelling of cardiac disease. This is of particular importance in the context of diabetic cardiomyopathy where diabetic individuals exhibit reduced cardiac diastolic contractile performance in the absence of vascular disease, significantly contributing towards high cardiovascular morbidity. In this study, the capacity of iPSC-CM to act as a novel cellular model of cardiomyocytes was assessed. The diabetic phenotype is characterised by insulin resistance, therefore there was a specific focus upon metabolic parameters. Despite expressing crucial insulin signalling intermediates and relevant trafficking proteins, it was identified that iPSC-CM do not exhibit insulin-stimulated glucose uptake. iPSC-CM are spontaneously contractile however contraction mediated uptake was not found to mask any insulin response. The fundamental limitation identified in these cells was a critical lack of expression of the insulin sensitive glucose transporter GLUT4. Using comparative immunoblot analysis and the GLUT-selective inhibitor BAY-876 to quantify expression of these transporters, we show that iPSC-CM express high levels of GLUT1 and low levels of GLUT4 compared to primary cardiomyocytes and cultured adipocytes. Interventions to overcome this limitation were unsuccessful. We suggest that the utility of iPSC-CMs to study cardiac metabolic disorders may be limited by their apparent foetal-like phenotype.
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Affiliation(s)
- Peter R T Bowman
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Godfrey L Smith
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Gwyn W Gould
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Fischer AW, Albers K, Schlein C, Sass F, Krott LM, Schmale H, Gordts PLSM, Scheja L, Heeren J. PID1 regulates insulin-dependent glucose uptake by controlling intracellular sorting of GLUT4-storage vesicles. Biochim Biophys Acta Mol Basis Dis 2019; 1865:1592-1603. [PMID: 30904610 PMCID: PMC6624118 DOI: 10.1016/j.bbadis.2019.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/28/2019] [Accepted: 03/19/2019] [Indexed: 12/26/2022]
Abstract
The phosphotyrosine interacting domain-containing protein 1 (PID1) serves as a cytosolic adaptor protein of the LDL receptor-related protein 1 (LRP1). By regulating its intracellular trafficking, PID1 controls the hepatic, LRP1-dependent clearance of pro-atherogenic lipoproteins. In adipose and muscle tissues, LRP1 is present in endosomal storage vesicles containing the insulin-responsive glucose transporter 4 (GLUT4). This prompted us to investigate whether PID1 modulates GLUT4 translocation and function via its interaction with the LRP1 cytosolic domain. We initially evaluated this in primary brown adipocytes as we observed an inverse correlation between brown adipose tissue glucose uptake and expression of LRP1 and PID1. Insulin stimulation in wild type brown adipocytes induced LRP1 and GLUT4 translocation from endosomal storage vesicles to the cell surface. Loss of PID1 expression in brown adipocytes prompted LRP1 and GLUT4 sorting to the plasma membrane independent of insulin signaling. When placed on a diabetogenic high fat diet, systemic and adipocyte-specific PID1-deficient mice presented with improved hyperglycemia and glucose tolerance as well as reduced basal plasma insulin levels compared to wild type control mice. Moreover, the improvements in glucose parameters associated with increased glucose uptake in adipose and muscle tissues from PID1-deficient mice. The data provide evidence that PID1 serves as an insulin-regulated retention adaptor protein controlling translocation of LRP1 in conjunction with GLUT4 to the plasma membrane of adipocytes. Notably, loss of PID1 corrects for insulin resistance-associated hyperglycemia emphasizing its pivotal role and therapeutic potential in the regulation of glucose homeostasis.
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Affiliation(s)
- Alexander W Fischer
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Kirstin Albers
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Christian Schlein
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Frederike Sass
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Lucia M Krott
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Hartwig Schmale
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Philip L S M Gordts
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ludger Scheja
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany.
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Huang X, Wu D, Cheng Y, Zhang X, Liu T, Liu Q, Xia P, Zhang G, Hu S, Liu S. Restoration of myocardial glucose uptake with facilitated myocardial glucose transporter 4 translocation contributes to alleviation of diabetic cardiomyopathy in rats after duodenal-jejunal bypass. J Diabetes Investig 2019; 10:626-638. [PMID: 30290074 PMCID: PMC6497603 DOI: 10.1111/jdi.12948] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 09/10/2018] [Accepted: 10/01/2018] [Indexed: 12/17/2022] Open
Abstract
AIMS/INTRODUCTION Duodenal-jejunal bypass (DJB) surgery has been reported to effectively relieve diabetic cardiomyopathy (DCM). However, the specific mechanisms remain largely unknown. The present study was designed to determine the alterations of myocardial glucose uptake (MGU) after DJB and their effects on DCM. MATERIALS AND METHODS Duodenal-jejunal bypass and sham surgeries were carried out in diabetic rats induced by a high-fat diet and a low dose of streptozotocin, with chow-diet fed rats as controls. Bodyweight, food intake, glucose homeostasis and lipid profiles were measured at indicated time-points. Cardiac function was evaluated by transthoracic echocardiography and hemodynamic measurement. Cardiac remodeling was assessed by a series of morphometric analyses along with transmission electron microscopy. Positron-emission tomography with fluorine-18 labeled fluorodeoxyglucose was carried out to evaluate the MGU in vivo. Furthermore, myocardial glucose transporters (GLUT; GLUT1 and GLUT4), myocardial insulin signaling and GLUT-4 translocation-related proteins were investigated to elucidate the underlying mechanisms. RESULTS The DJB group showed restored systolic and diastolic cardiac function, along with significant remission in cardiac hypertrophy, cardiac fibrosis, lipid deposit and ultrastructural disorder independent of weight loss compared with the sham group. Furthermore, the DJB group showed upregulated myocardial insulin signaling, hyperphosphorylation of AKT substrate of 160 kDa (AS160) and TBC1D1, along with preserved soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins, facilitating the GLUT-4 translocation to the myocardial cell surface and restoration of MGU. CONCLUSIONS The present findings provide evidence that restoration of MGU is implicated in the alleviation of DCM after DJB through facilitating GLUT-4 translocation, suggesting a potential choice for treatment of human DCM if properly implemented.
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Affiliation(s)
- Xin Huang
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Dong Wu
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Yugang Cheng
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Xiang Zhang
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Teng Liu
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Qiaoran Liu
- State Key Laboratory of Diabetes and Obesity SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Pingtian Xia
- State Key Laboratory of Diabetes and Obesity SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Guangyong Zhang
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Sanyuan Hu
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
| | - Shaozhuang Liu
- Department of General SurgeryQilu Hospital of Shandong UniversityJinanChina
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11
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Bowman PRT, Smith GL, Gould GW. Cardiac SNARE Expression in Health and Disease. Front Endocrinol (Lausanne) 2019; 10:881. [PMID: 31920989 PMCID: PMC6930865 DOI: 10.3389/fendo.2019.00881] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/03/2019] [Indexed: 12/16/2022] Open
Abstract
SNARE proteins are integral to intracellular vesicular trafficking, which in turn is the process underlying the regulated expression of substrate transporters such as the glucose transporter GLUT4 at the cell surface of insulin target tissues. Impaired insulin stimulated GLUT4 trafficking is associated with reduced cardiac function in many disease states, most notably diabetes. Despite this, our understanding of the expression and regulation of SNARE proteins in cardiac tissue and how these may change in diabetes is limited. Here we characterize the array of SNARE proteins expressed in cardiac tissue, and quantify the levels of expression of VAMP2, SNAP23, and Syntaxin4-key proteins involved in insulin-stimulated GLUT4 translocation. We examined SNARE protein levels in cardiac tissue from two rodent models of insulin resistance, db/db mice and high-fat fed mice, and show alterations in patterns of expression are evident. Such changes may have implications for cardiac function.
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Affiliation(s)
- Peter R. T. Bowman
- Henry Wellcome Laboratory of Cell Biology, College of Medical, Veterinary and Life Sciences, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Godfrey L. Smith
- College of Medical, Veterinary and Life Sciences, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Gwyn W. Gould
- Henry Wellcome Laboratory of Cell Biology, College of Medical, Veterinary and Life Sciences, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
- *Correspondence: Gwyn W. Gould
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12
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Jiao J, He M, Port SA, Baker RW, Xu Y, Qu H, Xiong Y, Wang Y, Jin H, Eisemann TJ, Hughson FM, Zhang Y. Munc18-1 catalyzes neuronal SNARE assembly by templating SNARE association. eLife 2018; 7:41771. [PMID: 30540253 PMCID: PMC6320071 DOI: 10.7554/elife.41771] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 12/11/2018] [Indexed: 01/16/2023] Open
Abstract
Sec1/Munc18-family (SM) proteins are required for SNARE-mediated membrane fusion, but their mechanism(s) of action remain controversial. Using single-molecule force spectroscopy, we found that the SM protein Munc18-1 catalyzes step-wise zippering of three synaptic SNAREs (syntaxin, VAMP2, and SNAP-25) into a four-helix bundle. Catalysis requires formation of an intermediate template complex in which Munc18-1 juxtaposes the N-terminal regions of the SNARE motifs of syntaxin and VAMP2, while keeping their C-terminal regions separated. SNAP-25 binds the templated SNAREs to induce full SNARE zippering. Munc18-1 mutations modulate the stability of the template complex in a manner consistent with their effects on membrane fusion, indicating that chaperoned SNARE assembly is essential for exocytosis. Two other SM proteins, Munc18-3 and Vps33, similarly chaperone SNARE assembly via a template complex, suggesting that SM protein mechanism is conserved.
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Affiliation(s)
- Junyi Jiao
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Mengze He
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Sarah A Port
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Richard W Baker
- Department of Molecular Biology, Princeton University, Princeton, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Yonggang Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Hong Qu
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Yujian Xiong
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Yukun Wang
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Huaizhou Jin
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Travis J Eisemann
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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13
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Tokarz VL, MacDonald PE, Klip A. The cell biology of systemic insulin function. J Cell Biol 2018; 217:2273-2289. [PMID: 29622564 PMCID: PMC6028526 DOI: 10.1083/jcb.201802095] [Citation(s) in RCA: 230] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 03/21/2018] [Accepted: 03/23/2018] [Indexed: 12/12/2022] Open
Abstract
Insulin is the paramount anabolic hormone, promoting carbon energy deposition in the body. Its synthesis, quality control, delivery, and action are exquisitely regulated by highly orchestrated intracellular mechanisms in different organs or "stations" of its bodily journey. In this Beyond the Cell review, we focus on these five stages of the journey of insulin through the body and the captivating cell biology that underlies the interaction of insulin with each organ. We first analyze insulin's biosynthesis in and export from the β-cells of the pancreas. Next, we focus on its first pass and partial clearance in the liver with its temporality and periodicity linked to secretion. Continuing the journey, we briefly describe insulin's action on the blood vasculature and its still-debated mechanisms of exit from the capillary beds. Once in the parenchymal interstitium of muscle and adipose tissue, insulin promotes glucose uptake into myofibers and adipocytes, and we elaborate on the intricate signaling and vesicle traffic mechanisms that underlie this fundamental function. Finally, we touch upon the renal degradation of insulin to end its action. Cellular discernment of insulin's availability and action should prove critical to understanding its pivotal physiological functions and how their failure leads to diabetes.
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Affiliation(s)
- Victoria L Tokarz
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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14
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Perrotta C, Cervia D, Di Renzo I, Moscheni C, Bassi MT, Campana L, Martelli C, Catalani E, Giovarelli M, Zecchini S, Coazzoli M, Capobianco A, Ottobrini L, Lucignani G, Rosa P, Rovere-Querini P, De Palma C, Clementi E. Nitric Oxide Generated by Tumor-Associated Macrophages Is Responsible for Cancer Resistance to Cisplatin and Correlated With Syntaxin 4 and Acid Sphingomyelinase Inhibition. Front Immunol 2018; 9:1186. [PMID: 29896202 PMCID: PMC5987706 DOI: 10.3389/fimmu.2018.01186] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 05/14/2018] [Indexed: 12/13/2022] Open
Abstract
Tumor microenvironment is fundamental for cancer progression and chemoresistance. Among stromal cells tumor-associated macrophages (TAMs) represent the largest population of infiltrating inflammatory cells in malignant tumors, promoting their growth, invasion, and immune evasion. M2-polarized TAMs are endowed with the nitric oxide (NO)-generating enzyme inducible nitric oxide synthase (iNOS). NO has divergent effects on tumors, since it can either stimulate tumor cells growth or promote their death depending on the source of it; likewise the role of iNOS in cancer differs depending on the cell type. The role of NO generated by TAMs has not been investigated. Using different tumor models in vitro and in vivo we found that NO generated by iNOS of M2-polarized TAMs is able to protect tumor cells from apoptosis induced by the chemotherapeutic agent cisplatin (CDDP). Here, we demonstrate that the protective effect of NO depends on the inhibition of acid sphingomyelinase (A-SMase), which is activated by CDDP in a pathway involving the death receptor CD95. Mechanistic insights indicate that NO actions occur via generation of cyclic GMP and activation of protein kinase G (PKG), inducing phosphorylation of syntaxin 4 (synt4), a SNARE protein responsible for A-SMase trafficking and activation. Noteworthy, phosphorylation of synt4 at serine 78 by PKG is responsible for the proteasome-dependent degradation of synt4, which limits the CDDP-induced exposure of A-SMase to the plasma membrane of tumor cells. This inhibits the cytotoxic mechanism of CDDP reducing A-SMase-triggered apoptosis. This is the first demonstration that endogenous NO system is a key mechanism through which TAMs protect tumor cells from chemotherapeutic drug-induced apoptosis. The identification of the pathway responsible for A-SMase activity downregulation in tumors leading to chemoresistance warrants further investigations as a means to identify new anti-cancer molecules capable of specifically inhibiting synt4 degradation.
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Affiliation(s)
- Cristiana Perrotta
- Department of Biomedical and Clinical Sciences "L. Sacco", Università degli Studi di Milano, Milan, Italy
| | - Davide Cervia
- Department for Innovation in Biological, Agro-Food and Forest Systems, Università degli Studi della Tuscia, Viterbo, Italy
| | - Ilaria Di Renzo
- Department of Biomedical and Clinical Sciences "L. Sacco", Università degli Studi di Milano, Milan, Italy
| | - Claudia Moscheni
- Department of Biomedical and Clinical Sciences "L. Sacco", Università degli Studi di Milano, Milan, Italy
| | | | - Lara Campana
- Division of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy.,Medical Research Council Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Cristina Martelli
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy
| | - Elisabetta Catalani
- Department for Innovation in Biological, Agro-Food and Forest Systems, Università degli Studi della Tuscia, Viterbo, Italy
| | - Matteo Giovarelli
- Department of Biomedical and Clinical Sciences "L. Sacco", Università degli Studi di Milano, Milan, Italy
| | - Silvia Zecchini
- Unit of Clinical Pharmacology, University Hospital "L. Sacco"-ASST Fatebenefratelli Sacco, Department of Biomedical and Clinical Sciences, CNR-Institute of Neuroscience, Università degli Studi di Milano, Milan, Italy
| | - Marco Coazzoli
- Department of Biomedical and Clinical Sciences "L. Sacco", Università degli Studi di Milano, Milan, Italy
| | - Annalisa Capobianco
- Division of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy
| | - Luisa Ottobrini
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.,CNR-Institute for Molecular Bioimaging and Physiology, Milan, Italy
| | - Giovanni Lucignani
- Department of Health Sciences, Università degli Studi di Milano, Milan, Italy
| | - Patrizia Rosa
- Department of Medical Biotechnologies and Translational Medicine Pharmacology, CNR-Institute of Neuroscience, Università degli Studi di Milano, Milan, Italy
| | - Patrizia Rovere-Querini
- Division of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milan, Italy.,Università Vita-Salute San Raffaele, Milan, Italy
| | - Clara De Palma
- Unit of Clinical Pharmacology, University Hospital "L. Sacco"-ASST Fatebenefratelli Sacco, Department of Biomedical and Clinical Sciences, CNR-Institute of Neuroscience, Università degli Studi di Milano, Milan, Italy
| | - Emilio Clementi
- "Eugenio Medea" Scientific Institute, Bosisio Parini, Italy.,Unit of Clinical Pharmacology, University Hospital "L. Sacco"-ASST Fatebenefratelli Sacco, Department of Biomedical and Clinical Sciences, CNR-Institute of Neuroscience, Università degli Studi di Milano, Milan, Italy
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15
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Abstract
In this chapter a detailed protocol of proximity ligation assay (PLA) is described thoroughly. PLA is a technique that allows detection of protein associations in situ, providing a sensitive and selective approach for protein-protein interaction studies. We demonstrate the technique by applying it for trafficking studies of the facilitative glucose transporter GLUT4. Trafficking of GLUT4 from perinuclear depots to the plasma membrane is regulated by insulin in adipocytes and muscle cells, and mediated by formation of functional SNARE complexes containing Syntaxin4, SNAP23, and VAMP2. The Sec1/Munc18 (SM) protein Munc18c also plays a key role in insulin-stimulated GLUT4 translocation via a series of different interactions with the SNARE complex and/or with the SNARE proteins individually. Studying the interactions that occur between SNARE proteins themselves and also with Munc18c in insulin-responsive cells is critical to further understand SNARE protein function and GLUT4 trafficking mechanism in general.
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16
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SNARE phosphorylation: a control mechanism for insulin-stimulated glucose transport and other regulated exocytic events. Biochem Soc Trans 2017; 45:1271-1277. [PMID: 29101310 DOI: 10.1042/bst20170202] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/03/2017] [Accepted: 10/04/2017] [Indexed: 11/17/2022]
Abstract
Trafficking within eukaryotic cells is a complex and highly regulated process; events such as recycling of plasma membrane receptors, formation of multivesicular bodies, regulated release of hormones and delivery of proteins to membranes all require directionality and specificity. The underpinning processes, including cargo selection, membrane fusion, trafficking flow and timing, are controlled by a variety of molecular mechanisms and engage multiple families of lipids and proteins. Here, we will focus on control of trafficking processes via the action of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) family of proteins, in particular their regulation by phosphorylation. We will describe how these proteins are controlled in a range of regulated trafficking events, with particular emphasis on the insulin-stimulated delivery of glucose transporters to the surface of adipose and muscle cells. Here, we focus on a few examples of SNARE phosphorylation which exemplify distinct ways in which SNARE machinery phosphorylation may regulate membrane fusion.
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17
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Jaldin-Fincati JR, Pavarotti M, Frendo-Cumbo S, Bilan PJ, Klip A. Update on GLUT4 Vesicle Traffic: A Cornerstone of Insulin Action. Trends Endocrinol Metab 2017; 28:597-611. [PMID: 28602209 DOI: 10.1016/j.tem.2017.05.002] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/08/2017] [Accepted: 05/09/2017] [Indexed: 12/20/2022]
Abstract
Glucose transport is rate limiting for dietary glucose utilization by muscle and fat. The glucose transporter GLUT4 is dynamically sorted and retained intracellularly and redistributes to the plasma membrane (PM) by insulin-regulated vesicular traffic, or 'GLUT4 translocation'. Here we emphasize recent findings in GLUT4 translocation research. The application of total internal reflection fluorescence microscopy (TIRFM) has increased our understanding of insulin-regulated events beneath the PM, such as vesicle tethering and membrane fusion. We describe recent findings on Akt-targeted Rab GTPase-activating proteins (GAPs) (TBC1D1, TBC1D4, TBC1D13) and downstream Rab GTPases (Rab8a, Rab10, Rab13, Rab14, and their effectors) along with the input of Rac1 and actin filaments, molecular motors [myosinVa (MyoVa), myosin1c (Myo1c), myosinIIA (MyoIIA)], and membrane fusion regulators (syntaxin4, munc18c, Doc2b). Collectively these findings reveal novel events in insulin-regulated GLUT4 traffic.
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Affiliation(s)
| | - Martin Pavarotti
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; IHEM, Universidad Nacional de Cuyo, CONICET, Mendoza 5500, Argentina
| | - Scott Frendo-Cumbo
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Philip J Bilan
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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18
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Spessott WA, Sanmillan ML, Kulkarni VV, McCormick ME, Giraudo CG. Syntaxin 4 mediates endosome recycling for lytic granule exocytosis in cytotoxic T-lymphocytes. Traffic 2017; 18:442-452. [PMID: 28471021 PMCID: PMC5513838 DOI: 10.1111/tra.12490] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 04/30/2017] [Accepted: 05/01/2017] [Indexed: 12/15/2022]
Abstract
Adaptive and innate immunity utilize the perforin-killing pathway to eliminate virus-infected or cancer cells. Cytotoxic T-lymphocytes (CTLs) and natural killer cells mediate this process by releasing toxic proteins at the contact area with target cells known as immunological synapse (IS). Formation of a stable IS and exocytosis of toxic proteins requires persistent fusion of Rab11a recycling endosomes with the plasma membrane (PM) that may assure the delivery of key effector proteins. Despite the importance of the recycling endosomal compartment, the membrane fusion proteins that control this process at the IS remain elusive. Here, by performing knockdown experiments we found that syntaxin 4 (STX4) is necessary for cytotoxic activity and CD107a degranulation against target cells in a similar fashion to syntaxin 11, which is involved in lytic granule (LG) exocytosis and immunodeficiency when it is mutated. Using total internal reflection fluorescent microscopy we identified that STX4 mediates fusion of EGFP-Rab11a vesicles at the IS. Immunoprecipitation experiments in lysates of activated CTLs indicate that endogenous STX4 may drive this fusion step by interacting with cognate proteins: Munc18-3/SNAP23/VAMP7 and/or VAMP8. These results reveal the role of STX4 in mediating fusion of Rab11a endosomes upstream of lytic granules (LGs) exocytosis and further demonstrate the importance of this pathway in controlling CTL-mediated cytotoxicity.
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Affiliation(s)
- Waldo A. Spessott
- Department of Pathology and Laboratory Medicine, University of Pennsylvania – The Children’s Hospital of Philadelphia - 3615 Civic Center Blvd, Philadelphia PA, 19104
| | - Maria L. Sanmillan
- Department of Pathology and Laboratory Medicine, University of Pennsylvania – The Children’s Hospital of Philadelphia - 3615 Civic Center Blvd, Philadelphia PA, 19104
| | - Vineet V. Kulkarni
- Department of Pathology and Laboratory Medicine, University of Pennsylvania – The Children’s Hospital of Philadelphia - 3615 Civic Center Blvd, Philadelphia PA, 19104
- Biomedical Graduate Studies- University of Pennsylvania
| | - Margaret E. McCormick
- Department of Pathology and Laboratory Medicine, University of Pennsylvania – The Children’s Hospital of Philadelphia - 3615 Civic Center Blvd, Philadelphia PA, 19104
| | - Claudio G. Giraudo
- Department of Pathology and Laboratory Medicine, University of Pennsylvania – The Children’s Hospital of Philadelphia - 3615 Civic Center Blvd, Philadelphia PA, 19104
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19
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Shamni O, Cohen G, Gruzman A, Zaid H, Klip A, Cerasi E, Sasson S. Regulation of GLUT4 activity in myotubes by 3-O-methyl-d-glucose. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017. [PMID: 28648676 DOI: 10.1016/j.bbamem.2017.06.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rate of glucose influx to skeletal muscles is determined primarily by the number of functional units of glucose transporter-4 (GLUT4) in the myotube plasma membrane. The abundance of GLUT4 in the plasma membrane is tightly regulated by insulin or contractile activity, which employ distinct pathways to translocate GLUT4-rich vesicles from intracellular compartments. Various studies have indicated that GLUT4 intrinsic activity is also regulated by conformational changes and/or interactions with membrane components and intracellular proteins in the vicinity of the plasma membrane. Here we show that the non-metabolizable glucose analog 3-O-methyl-d-glucose (MeGlc) augmented the rate of hexose transport into myotubes by increasing GLUT4 intrinsic activity without altering the content of the transporter in the plasma membrane. This effect was not a consequence of ATP depletion or hyperosmolar stress and did not involve Akt/PKB or AMPK signal transduction pathways. MeGlc reduced the inhibitory potency (increased Ki) of indinavir, a selective inhibitor of GLUT4, in a dose-dependent manner. Kinetic analyses indicate that MeGlc induced changes in GLUT4 or GLUT4 complexes within the plasma membrane, which enhanced the hexose transport activity and reduced the potency of indinavir inhibition. Finally, we present a simple kinetic analysis for screening and discovering low molecular weight compounds that augment GLUT4 activity.
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Affiliation(s)
- Ofer Shamni
- Department of Nuclear Medicine, the Hebrew University-Hadassah Medical Center, Jerusalem 9112001, Israel; Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel
| | - Guy Cohen
- The Skin Research Institute, The Dead-Sea & Arava Science Center, Israel; Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel
| | - Arie Gruzman
- Division of Medicinal Chemistry, Dept. of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel; Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel
| | - Hilal Zaid
- Al-Qasemi Research Center, Al-Qasemi Academy, Baqa-El-Gharbia 3010000, Israel; Program in Cell Biology, Hospital for Sick Children, Toronto, OT M5G 1XB, Canada
| | - Amira Klip
- Program in Cell Biology, Hospital for Sick Children, Toronto, OT M5G 1XB, Canada
| | - Erol Cerasi
- Endocrinology and Metabolism Service, Department of Internal Medicine, The Hebrew University-Hadassah Medical Center, Jerusalem 9112001, Israel
| | - Shlomo Sasson
- Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel.
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20
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Bergqvist N, Nyman E, Cedersund G, Stenkula KG. A systems biology analysis connects insulin receptor signaling with glucose transporter translocation in rat adipocytes. J Biol Chem 2017; 292:11206-11217. [PMID: 28495883 DOI: 10.1074/jbc.m117.787515] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 05/03/2017] [Indexed: 12/26/2022] Open
Abstract
Type 2 diabetes is characterized by insulin resistance, which arises from malfunctions in the intracellular insulin signaling network. Knowledge of the insulin signaling network is fragmented, and because of the complexity of this network, little consensus has emerged for the structure and importance of the different branches of the network. To help overcome this complexity, systems biology mathematical models have been generated for predicting both the activation of the insulin receptor (IR) and the redistribution of glucose transporter 4 (GLUT4) to the plasma membrane. Although the insulin signal transduction between IR and GLUT4 has been thoroughly studied with modeling and time-resolved data in human cells, comparable analyses in cells from commonly used model organisms such as rats and mice are lacking. Here, we combined existing data and models for rat adipocytes with new data collected for the signaling network between IR and GLUT4 to create a model also for their interconnections. To describe all data (>140 data points), the model needed three distinct pathways from IR to GLUT4: (i) via protein kinase B (PKB) and Akt substrate of 160 kDa (AS160), (ii) via an AS160-independent pathway from PKB, and (iii) via an additional pathway from IR, e.g. affecting the membrane constitution. The developed combined model could describe data not used for training the model and was used to generate predictions of the relative contributions of the pathways from IR to translocation of GLUT4. The combined model provides a systems-level understanding of insulin signaling in rat adipocytes, which, when combined with corresponding models for human adipocytes, may contribute to model-based drug development for diabetes.
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Affiliation(s)
| | - Elin Nyman
- From the Departments of Biomedical Engineering and.,Cardiovascular and Metabolic Diseases Innovative Medicines and Early Development Biotech Unit, AstraZeneca R&D, SE431 83 Gothenburg, Sweden, and
| | - Gunnar Cedersund
- From the Departments of Biomedical Engineering and .,Clinical and Experimental Medicine and Biomedical Engineering, Linköping University, SE581 85 Linköping, Sweden
| | - Karin G Stenkula
- Glucose Transport and Protein Trafficking, Department of Experimental Medical Sciences, Biomedical Centre, Lund University, SE221 84 Lund, Sweden
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21
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Zhou X, Shentu P, Xu Y. Spatiotemporal Regulators for Insulin-Stimulated GLUT4 Vesicle Exocytosis. J Diabetes Res 2017; 2017:1683678. [PMID: 28529958 PMCID: PMC5424486 DOI: 10.1155/2017/1683678] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/21/2017] [Accepted: 04/03/2017] [Indexed: 11/30/2022] Open
Abstract
Insulin increases glucose uptake and storage in muscle and adipose cells, which is accomplished through the mobilization of intracellular GLUT4 storage vesicles (GSVs) to the cell surface upon stimulation. Importantly, the dysfunction of insulin-regulated GLUT4 trafficking is strongly linked with peripheral insulin resistance and type 2 diabetes in human. The insulin signaling pathway, key signaling molecules involved, and precise trafficking itinerary of GSVs are largely identified. Understanding the interaction between insulin signaling molecules and key regulatory proteins that are involved in spatiotemporal regulation of GLUT4 vesicle exocytosis is of great importance to explain the pathogenesis of diabetes and may provide new potential therapeutic targets.
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Affiliation(s)
- Xiaoxu Zhou
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Ping Shentu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
- *Yingke Xu:
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22
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Sadler JBA, Roccisana J, Virolainen M, Bryant NJ, Gould GW. mVps45 knockdown selectively modulates VAMP expression in 3T3-L1 adipocytes. Commun Integr Biol 2015; 8:e1026494. [PMID: 26479872 PMCID: PMC4594494 DOI: 10.1080/19420889.2015.1026494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 08/05/2014] [Accepted: 08/06/2014] [Indexed: 02/08/2023] Open
Abstract
Insulin stimulates the delivery of glucose transporter-4 (GLUT4)-containing vesicles to the surface of adipocytes. Depletion of the Sec1/Munc18 protein mVps45 significantly abrogates insulin-stimulated glucose transport and GLUT4 translocation. Here we show that depletion of mVps45 selectively reduced expression of VAMPs 2 and 4, but not other VAMP isoforms. Although we did not observe direct interaction of mVps45 with any VAMP isoform; we found that the cognate binding partner of mVps45, Syntaxin 16 associates with VAMPs 2, 4, 7 and 8 in vitro. Co-immunoprecipitation experiments in 3T3-L1 adipocytes revealed an interaction between Syntaxin 16 and only VAMP4. We suggest GLUT4 trafficking is controlled by the coordinated expression of mVps45/Syntaxin 16/VAMP4, and that depletion of mVps45 regulates VAMP2 levels indirectly, perhaps via reduced trafficking into specialized subcellular compartments.
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Affiliation(s)
- Jessica B A Sadler
- Henry Wellcome Laboratory of Cell Biology; Institute of Molecular; Cell and Systems Biology; College of Medical; Veterinary and Life Sciences; University of Glasgow ; Glasgow, Scotland
| | - Jennifer Roccisana
- Henry Wellcome Laboratory of Cell Biology; Institute of Molecular; Cell and Systems Biology; College of Medical; Veterinary and Life Sciences; University of Glasgow ; Glasgow, Scotland
| | - Minttu Virolainen
- Henry Wellcome Laboratory of Cell Biology; Institute of Molecular; Cell and Systems Biology; College of Medical; Veterinary and Life Sciences; University of Glasgow ; Glasgow, Scotland
| | - Nia J Bryant
- Department of Biology; University of York ; Heslington, York
| | - Gwyn W Gould
- Henry Wellcome Laboratory of Cell Biology; Institute of Molecular; Cell and Systems Biology; College of Medical; Veterinary and Life Sciences; University of Glasgow ; Glasgow, Scotland
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23
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TUSC5 regulates insulin-mediated adipose tissue glucose uptake by modulation of GLUT4 recycling. Mol Metab 2015; 4:795-810. [PMID: 26629404 PMCID: PMC4632119 DOI: 10.1016/j.molmet.2015.08.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 08/11/2015] [Accepted: 08/18/2015] [Indexed: 12/26/2022] Open
Abstract
Objective Failure to properly dispose of glucose in response to insulin is a serious health problem, occurring during obesity and is associated with type 2 diabetes development. Insulin-stimulated glucose uptake is facilitated by the translocation and plasma membrane fusion of vesicles containing glucose transporter 4 (GLUT4), the rate-limiting step of post-prandial glucose disposal. Methods We analyzed the role of Tusc5 in the regulation of insulin-stimulated Glut4-mediated glucose uptake in vitro and in vivo. Furthermore, we measured Tusc5 expression in two patient cohorts. Results Herein, we report that TUSC5 controls insulin-stimulated glucose uptake in adipocytes, in vitro and in vivo. TUSC5 facilitates the proper recycling of GLUT4 and other key trafficking proteins during prolonged insulin stimulation, thereby enabling proper protein localization and complete vesicle formation, processes that ultimately enable insulin-stimulated glucose uptake. Tusc5 knockout mice exhibit impaired glucose disposal and TUSC5 expression is predictive of glucose tolerance in obese individuals, independent of body weight. Furthermore, we show that TUSC5 is a PPARγ target and in its absence the anti-diabetic effects of TZDs are significantly blunted. Conclusions Collectively, these findings establish TUSC5 as an adipose tissue-specific protein that enables proper protein recycling, linking the ubiquitous vesicle traffic machinery with tissue-specific insulin-mediated glucose uptake into adipose tissue and the maintenance of a healthy metabolic phenotype in mice and humans. Tusc5 regulates glucose uptake in adipose tissue by modulating the GSV recycling machinery. Tusc5 knockout mice develop insulin resistance due to impaired adipose tissue glucose uptake. Rosiglitazone improves glucose homeostasis in part through the induction of Tusc5. Tusc5 is a novel adipose specific adaptor protein linking Glut4 trafficking to the ubiquitous machinery.
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Kioumourtzoglou D, Pryor PR, Gould GW, Bryant NJ. Alternative routes to the cell surface underpin insulin-regulated membrane trafficking of GLUT4. J Cell Sci 2015; 128:2423-9. [PMID: 26071524 PMCID: PMC4510850 DOI: 10.1242/jcs.166561] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 05/26/2015] [Indexed: 01/12/2023] Open
Abstract
Insulin-stimulated delivery of glucose transporters (GLUT4, also known as SLC2A4) from specialized intracellular GLUT4 storage vesicles (GSVs) to the surface of fat and muscle cells is central to whole-body glucose regulation. This translocation and subsequent internalization of GLUT4 back into intracellular stores transits through numerous small membrane-bound compartments (internal GLUT4-containing vesicles; IGVs) including GSVs, but the function of these different compartments is not clear. Cellugyrin (also known as synaptogyrin-2) and sortilin define distinct populations of IGV; sortilin-positive IGVs represent GSVs, but the function of cellugyrin-containing IGVs is unknown. Here, we demonstrate a role for cellugyrin in intracellular sequestration of GLUT4 in HeLa cells and have used a proximity ligation assay to follow changes in pairwise associations between cellugyrin, sortilin, GLUT4 and membrane trafficking machinery following insulin-stimulation of 3T3-L1 adipoctyes. Our data suggest that insulin stimulates traffic from cellugyrin-containing to sortilin-containing membranes, and that cellugyrin-containing IGVs provide an insulin-sensitive reservoir to replenish GSVs following insulin-stimulated exocytosis of GLUT4. Furthermore, our data support the existence of a pathway from cellugyrin-containing membranes to the surface of 3T3-L1 adipocytes that bypasses GSVs under basal conditions, and that insulin diverts traffic away from this into GSVs.
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Affiliation(s)
- Dimitrios Kioumourtzoglou
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK Department of Biology, University of York, York YO10 5DD, UK
| | - Paul R Pryor
- Department of Biology, University of York, York YO10 5DD, UK Centre for Immunology and Infection, Hull York Medical School, University of York, York YO10 5DD, UK
| | - Gwyn W Gould
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Nia J Bryant
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK Department of Biology, University of York, York YO10 5DD, UK
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Grubišić V, Parpura V. Diversity in the utilization of glucose and lactate in synthetic mammalian myotubes generated by engineered configurations of MyoD and E12 in otherwise non-differentiation growth conditions. Biomaterials 2014; 43:50-60. [PMID: 25591961 DOI: 10.1016/j.biomaterials.2014.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 12/03/2014] [Indexed: 12/21/2022]
Abstract
We previously used the expression of various combinations and configurations of MyoD and E12, two basic helix-loop-helix transcription factors (TF), to produce populations of myotubes assuming distinct morphology, myofibrillar development and Ca2+ dynamics, from mammalian C2C12 myoblasts in non-differentiation growth conditions. Here, we assessed the synthetically generated myotubes in terms of energetics, otherwise necessary to sustain their mechanical output as bio-actuators. We found that the myotubes exhibit changed expression of key regulators for the uptake and utilization of two major cellular fuels, glucose and lactate. Furthermore, while lactate transport was uniformly slowed in all the populations of myotubes, glucose uptake and utilization were modified by particular TF configuration. Our approach allows the production of a class of biomaterials with predetermined energetics that could be applied in biorobotics, where fuel of choice could be used, and also in reparative medicine where, for example, particular population of myotubes could be additionally employed as glucose sinks to mitigate effects of secondary metabolic syndrome.
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Affiliation(s)
- Vladimir Grubišić
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Vladimir Parpura
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia.
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Expression of syntaxin 8 in visceral adipose tissue is increased in obese patients with type 2 diabetes and related to markers of insulin resistance and inflammation. Arch Med Res 2014; 46:47-53. [PMID: 25523146 DOI: 10.1016/j.arcmed.2014.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 12/09/2014] [Indexed: 11/22/2022]
Abstract
BACKGROUND AND AIMS Obesity is associated with increased adipose tissue inflammation as well as with the development of type 2 diabetes (T2D). Syntaxin 8 (STX8) is a protein required for the transport of endosomes. In this study we analyzed the relationship of STX8 with the presence of T2D in the context of obesity. METHODS With this purpose, 21 subjects (seven lean [LN], eight obese normoglycemic [OB-NG] and six obese with type 2 diabetes [OB-T2D]) were included in the study. Gene and protein expression levels of STX8 and GLUT4 were analyzed in visceral adipose tissue (VAT). RESULTS mRNA (p = 0.008) and protein (p <0.001) expression levels of STX8 were significantly increased in VAT of OB-T2D patients. Moreover, gene expression levels of SLC2A4 (GLUT4) were downregulated (p = 0.002) in VAT of obese patients. We found that STX8 was positively correlated (p <0.05) with fasting glucose concentrations, plasma glucose 2 h after an OGTT and C-reactive protein. Interestingly, the expression of STX8 was negatively correlated (p <0.05) with the expression of SLC2A4 in VAT. CONCLUSIONS Increased STX8 expression in VAT appears to be associated with the presence of T2D in obese patients through a mechanism that may involve GLUT4.
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Sadler JBA, Bryant NJ, Gould GW. Characterization of VAMP isoforms in 3T3-L1 adipocytes: implications for GLUT4 trafficking. Mol Biol Cell 2014; 26:530-6. [PMID: 25501368 PMCID: PMC4310743 DOI: 10.1091/mbc.e14-09-1368] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The levels of expression, distribution, and association of all of the VAMPs expressed in 3T3-L1 adipocytes are characterized. This is the first systematic analysis of all members of this protein family for any cell type. The fusion of GLUT4-containing vesicles with the plasma membrane of adipocytes is a key facet of insulin action. This process is mediated by the formation of functional soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes between the plasma membrane t-SNARE complex and the vesicle v-SNARE or VAMP. The t-SNARE complex consists of Syntaxin4 and SNAP23, and whereas many studies identify VAMP2 as the v-SNARE, others suggest that either VAMP3 or VAMP8 may also fulfil this role. Here we characterized the levels of expression, distribution, and association of all the VAMPs expressed in 3T3-L1 adipocytes to provide the first systematic analysis of all members of this protein family for any cell type. Despite our finding that all VAMP isoforms form SDS-resistant SNARE complexes with Syntaxin4/SNAP23 in vitro, a combination of levels of expression (which vary by >30-fold), subcellular distribution, and coimmunoprecipitation analyses lead us to propose that VAMP2 is the major v-SNARE involved in GLUT4 trafficking to the surface of 3T3-L1 adipocytes.
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Affiliation(s)
- Jessica B A Sadler
- Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Nia J Bryant
- Department of Biology, University of York, Heslington YO10 5DD, United Kingdom
| | - Gwyn W Gould
- Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Ramalingam L, Yoder SM, Oh E, Thurmond DC. Munc18c: a controversial regulator of peripheral insulin action. Trends Endocrinol Metab 2014; 25:601-8. [PMID: 25028245 PMCID: PMC4253632 DOI: 10.1016/j.tem.2014.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/12/2014] [Accepted: 06/20/2014] [Indexed: 12/19/2022]
Abstract
Insulin resistance, a hallmark of impaired glucose tolerance and type 2 diabetes (T2D), arises from dysfunction of insulin action and subsequent glucose uptake by peripheral tissues, predominantly skeletal muscle and fat. Exocytosis of glucose transporter (GLUT4)-containing vesicles facilitated by soluble NSF (N-ethylmaleimide-sensitive factor) attachment receptor (SNARE) protein isoforms, and Munc18c (mammalian homolog of Unc-18c) mediates this glucose uptake. Emerging evidences, including recent human clinical studies, point to pivotal roles for Munc18c in peripheral insulin action in adipose and skeletal muscle. Intriguing new advances are also initiating debates regarding the molecular mechanism(s) controlling Munc18c action. The objective of this review is therefore to present a balanced perspective of new continuities and controversies surrounding the regulation and requirement for Munc18c in the regulation of peripheral insulin action.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Stephanie M Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Eunjin Oh
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Debbie C Thurmond
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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29
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Kioumourtzoglou D, Sadler JBA, Black HL, Berends R, Wellburn C, Bryant NJ, Gould GW. Studies of the regulated assembly of SNARE complexes in adipocytes. Biochem Soc Trans 2014; 42:1396-400. [PMID: 25233421 DOI: 10.1042/bst20140114] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2024]
Abstract
Insulin plays a fundamental role in whole-body glucose homeostasis. Central to this is the hormone's ability to rapidly stimulate the rate of glucose transport into adipocytes and muscle cells [1]. Upon binding its receptor, insulin stimulates an intracellular signalling cascade that culminates in redistribution of glucose transporter proteins, specifically the GLUT4 isoform, from intracellular stores to the plasma membrane, a process termed 'translocation' [1,2]. This is an example of regulated membrane trafficking [3], a process that also underpins other aspects of physiology in a number of specialized cell types, for example neurotransmission in brain/neurons and release of hormone-containing vesicles from specialized secretory cells such as those found in pancreatic islets. These processes invoke a number of intriguing biological questions as follows. How is the machinery involved in these membrane trafficking events mobilized in response to a stimulus? How do the signalling pathways that detect the external stimulus interface with the trafficking machinery? Recent studies of insulin-stimulated GLUT4 translocation offer insight into such questions. In the present paper, we have reviewed these studies and draw parallels with other regulated trafficking systems.
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Affiliation(s)
- Dimitrios Kioumourtzoglou
- *Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, Davidson Building, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Jessica B A Sadler
- *Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, Davidson Building, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Hannah L Black
- †Department of Biology, University of York, Heslington, York YO10 5DD, U.K
| | - Rebecca Berends
- *Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, Davidson Building, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Cassie Wellburn
- *Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, Davidson Building, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Nia J Bryant
- †Department of Biology, University of York, Heslington, York YO10 5DD, U.K
| | - Gwyn W Gould
- *Henry Wellcome Laboratory of Cell Biology, Institute for Molecular, Cell and Systems Biology, Davidson Building, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K
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30
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van Oort MM, Drost R, Janβen L, Van Doorn JM, Kerver J, Van der Horst DJ, Luiken JJFP, Rodenburg KCW. Each of the four intracellular cysteines of CD36 is essential for insulin- or AMP-activated protein kinase-induced CD36 translocation. Arch Physiol Biochem 2014; 120:40-9. [PMID: 24377880 DOI: 10.3109/13813455.2013.876049] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Stimulation of cellular fatty acid uptake by induction of insulin signalling or AMP-kinase (AMPK) activation is due to translocation of the fatty acid-transporter CD36 from intracellular stores to the plasma membrane (PM). For investigating the role of the four Cys-residues within CD36's cytoplasmic tails in CD36 translocation, we constructed CHO-cells expressing CD36 mutants in which all four, two, or one of the intracellular Cys were replaced by Ser. Intracellular and PM localization of all mutants was similar to wild-type CD36 (CD36wt). Hence, the four Cys do not regulate sub-cellular CD36 localization. However, in contrast to CD36wt, insulin or AMPK activation failed to induce translocation of any of the mutants, indicating that all four intracellular Cys residues are essential for CD36 translocation. The mechanism of defective translocation of mutant CD36 is unknown, but appears not due to loss of S-palmitoylation of the cytoplasmic tails or to aberrant oligomerization of the mutants.
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Affiliation(s)
- Masja M van Oort
- Division of Endocrinology and Metabolism, Department of Biology and Institute of Biomembranes, Utrecht University , NL-3584 CH Utrecht , The Netherlands and
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31
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Insulin stimulates syntaxin4 SNARE complex assembly via a novel regulatory mechanism. Mol Cell Biol 2014; 34:1271-9. [PMID: 24469400 DOI: 10.1128/mcb.01203-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Insulin stimulates glucose transport into fat and muscle cells by increasing the exocytic trafficking rate of the GLUT4 facilitative glucose transporter from intracellular stores to the plasma membrane. Delivery of GLUT4 to the plasma membrane is mediated by formation of functional SNARE complexes containing syntaxin4, SNAP23, and VAMP2. Here we have used an in situ proximity ligation assay to integrate these two observations by demonstrating for the first time that insulin stimulation causes an increase in syntaxin4-containing SNARE complex formation in adipocytes. Furthermore, we demonstrate that insulin brings about this increase in SNARE complex formation by mobilizing a pool of syntaxin4 held in an inactive state under basal conditions. Finally, we have identified phosphorylation of the regulatory protein Munc18c, a direct target of the insulin receptor, as a molecular switch to coordinate this process. Hence, this report provides molecular detail of how the cell alters membrane traffic in response to an external stimulus, in this case, insulin.
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32
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Rehman A, Jarrott RJ, Whitten AE, King GJ, Hu SH, Christie MP, Collins BM, Martin JL. Milligram quantities of homogeneous recombinant full-length mouse Munc18c from Escherichia coli cultures. PLoS One 2013; 8:e83499. [PMID: 24391775 PMCID: PMC3877047 DOI: 10.1371/journal.pone.0083499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 11/05/2013] [Indexed: 12/24/2022] Open
Abstract
Vesicle fusion is an indispensable cellular process required for eukaryotic cargo delivery. The Sec/Munc18 protein Munc18c is essential for insulin-regulated trafficking of glucose transporter4 (GLUT4) vesicles to the cell surface in muscle and adipose tissue. Previously, our biophysical and structural studies have used Munc18c expressed in SF9 insect cells. However to maximize efficiency, minimize cost and negate any possible effects of post-translational modifications of Munc18c, we investigated the use of Escherichia coli as an expression host for Munc18c. We were encouraged by previous reports describing Munc18c production in E. coli cultures for use in in vitro fusion assay, pulldown assays and immunoprecipitations. Our approach differs from the previously reported method in that it uses a codon-optimized gene, lower temperature expression and autoinduction media. Three N-terminal His-tagged constructs were engineered, two with a tobacco etch virus (TEV) or thrombin protease cleavage site to enable removal of the fusion tag. The optimized protocol generated 1–2 mg of purified Munc18c per L of culture at much reduced cost compared to Munc18c generated using insect cell culture. The purified recombinant Munc18c protein expressed in bacteria was monodisperse, monomeric, and functional. In summary, we developed methods that decrease the cost and time required to generate functional Munc18c compared with previous insect cell protocols, and which generates sufficient purified protein for structural and biophysical studies.
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Affiliation(s)
- Asma Rehman
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Russell J. Jarrott
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Andrew E. Whitten
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Gordon J. King
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Shu-Hong Hu
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Michelle P. Christie
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Brett M. Collins
- Division of Molecular Cell Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
| | - Jennifer L. Martin
- Division of Chemistry and Structural Biology, University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia
- * E-mail:
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Senthivinayagam S, McIntosh AL, Moon KC, Atshaves BP. Plin2 inhibits cellular glucose uptake through interactions with SNAP23, a SNARE complex protein. PLoS One 2013; 8:e73696. [PMID: 24040030 PMCID: PMC3765312 DOI: 10.1371/journal.pone.0073696] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 07/25/2013] [Indexed: 11/19/2022] Open
Abstract
Although a link between excess lipid storage and aberrant glucose metabolism has been recognized for many years, little is known what role lipid storage droplets and associated proteins such as Plin2 play in managing cellular glucose levels. To address this issue, the influence of Plin2 on glucose uptake was examined using 2-NBD-Glucose and [(3)H]-2-deoxyglucose to show that insulin-mediated glucose uptake was decreased 1.7- and 1.8-fold, respectively in L cell fibroblasts overexpressing Plin2. Conversely, suppression of Plin2 levels by RNAi-mediated knockdown increased 2-NBD-Glucose uptake several fold in transfected L cells and differentiated 3T3-L1 cells. The effect of Plin2 expression on proteins involved in glucose uptake and transport was also examined. Expression of the SNARE protein SNAP23 was increased 1.6-fold while levels of syntaxin-5 were decreased 1.7-fold in Plin2 overexpression cells with no significant changes observed in lipid droplet associated proteins Plin1 or FSP27 or with the insulin receptor, GLUT1, or VAMP4. FRET experiments revealed a close proximity of Plin2 to SNAP23 on lipid droplets to within an intramolecular distance of 51 Å. The extent of targeting of SNAP23 to lipid droplets was determined by co-localization and co-immunoprecipitation experiments to show increased partitioning of SNAP23 to lipid droplets when Plin2 was overexpressed. Taken together, these results suggest that Plin2 inhibits glucose uptake by interacting with, and regulating cellular targeting of SNAP23 to lipid droplets. In summary, the current study for the first time provides direct evidence for the role of Plin2 in mediating cellular glucose uptake.
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Affiliation(s)
- Subramanian Senthivinayagam
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Avery L. McIntosh
- Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas, United States of America
| | - Kenneth C. Moon
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Barbara P. Atshaves
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
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Roccisana J, Sadler JBA, Bryant NJ, Gould GW. Sorting of GLUT4 into its insulin-sensitive store requires the Sec1/Munc18 protein mVps45. Mol Biol Cell 2013; 24:2389-97. [PMID: 23741049 PMCID: PMC3727931 DOI: 10.1091/mbc.e13-01-0011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 05/24/2013] [Accepted: 05/29/2013] [Indexed: 01/15/2023] Open
Abstract
Insulin stimulates glucose transport in fat and muscle cells by regulating delivery of the facilitative glucose transporter, glucose transporter isoform 4 (GLUT4), to the plasma membrane. In the absence of insulin, GLUT4 is sequestered away from the general recycling endosomal pathway into specialized vesicles, referred to as GLUT4-storage vesicles. Understanding the sorting of GLUT4 into this store is a major challenge. Here we examine the role of the Sec1/Munc18 protein mVps45 in GLUT4 trafficking. We show that mVps45 is up-regulated upon differentiation of 3T3-L1 fibroblasts into adipocytes and is expressed at stoichiometric levels with its cognate target-soluble N-ethylmaleimide-sensitive factor attachment protein receptor, syntaxin 16. Depletion of mVps45 in 3T3-L1 adipocytes results in decreased GLUT4 levels and impaired insulin-stimulated glucose transport. Using sub-cellular fractionation and an in vitro assay for GLUT4-storage vesicle formation, we show that mVps45 is required to correctly traffic GLUT4 into this compartment. Collectively our data reveal a crucial role for mVps45 in the delivery of GLUT4 into its specialized, insulin-regulated compartment.
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Affiliation(s)
- Jennifer Roccisana
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Jessica B. A. Sadler
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Nia J. Bryant
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Gwyn W. Gould
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Sadler JBA, Bryant NJ, Gould GW, Welburn CR. Posttranslational modifications of GLUT4 affect its subcellular localization and translocation. Int J Mol Sci 2013; 14:9963-78. [PMID: 23665900 PMCID: PMC3676823 DOI: 10.3390/ijms14059963] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/02/2013] [Accepted: 05/02/2013] [Indexed: 01/05/2023] Open
Abstract
The facilitative glucose transporter type 4 (GLUT4) is expressed in adipose and muscle and plays a vital role in whole body glucose homeostasis. In the absence of insulin, only ~1% of cellular GLUT4 is present at the plasma membrane, with the vast majority localizing to intracellular organelles. GLUT4 is retained intracellularly by continuous trafficking through two inter-related cycles. GLUT4 passes through recycling endosomes, the trans Golgi network and an insulin-sensitive intracellular compartment, termed GLUT4-storage vesicles or GSVs. It is from GSVs that GLUT4 is mobilized to the cell surface in response to insulin, where it increases the rate of glucose uptake into the cell. As with many physiological responses to external stimuli, this regulated trafficking event involves multiple posttranslational modifications. This review outlines the roles of posttranslational modifications of GLUT4 on its function and insulin-regulated trafficking.
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Affiliation(s)
| | - Nia J. Bryant
- Institute of Molecular, Cell and Systems Biology, Davidson Building, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; E-Mails: (J.B.A.S.); (N.J.B.); (G.W.G.)
| | - Gwyn W. Gould
- Institute of Molecular, Cell and Systems Biology, Davidson Building, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; E-Mails: (J.B.A.S.); (N.J.B.); (G.W.G.)
| | - Cassie R. Welburn
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +44-141-330-6454; Fax: +44-141-330-5481
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Shi FH, Wu Y, Dai DZ, Cong XD, Zhang YM, Dai Y. Hepatosteatosis and hepatic insulin resistance are blunted by argirein, an anti-inflammatory agent, through normalizing endoplasmic reticulum stress and apoptosis in diabetic liver. ACTA ACUST UNITED AC 2013; 65:916-27. [PMID: 23647685 DOI: 10.1111/jphp.12051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 02/11/2013] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Insulin resistance represents a mechanism underlying defect metabolism of carbohydrate and lipid linked to inflammatory reactions in diabetic liver. We hypothesized that the changes may be secondary to endoplasmic reticulum (ER) stress, which could be alleviated by either argirein or valsartan. METHODS Hepatosteatosis in diabetic liver was induced in rats fed with a high-fat diet (HFD) for 12 weeks combined with a single low dose of streptozotocin (STZ 35 mg/kg, ip). Interventions (mg/kg/d, po)with either argirein (50, 100 and 200) or valsartan (12) were conducted in the last 4 weeks. KEY FINDINGS In diabetic liver fat was significantly accumulated in association with elevated hepatic glucose, serum insulin and homeostasis model assessment of insulin resistance value. Downregulated glucose transporter 4, insulin receptor substrate-1 and leptin receptor (P < 0.01) were found relative to normal, where DNA ladder, downregulated B cell lymphoma/leukemia-2, upregulated B cell lymphoma/leukemia-2 Associated X protein and upregulated ER stress chaperones such as Bip/GRP78 (also known as Binding Protein, BiP), PKR-like ER kinase (PERK), p-PERK/PERK and C/EBP homologous protein were significant. These abnormalities were significantly ameliorated by argirein and valsartan. CONCLUSIONS Hepatosteatosis induced by HFD/low STZ manifests insulin resistance and apoptosis, linked to an entity of low-grade inflammation due to activated ER stress sensors. With anti-inflammatory activity either argirein or valsartan blunts hepatosteatosis through normalizing ER stress and apoptosis in the diabetic liver.
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Affiliation(s)
- Fang-Hong Shi
- China Pharmaceutical University, Research Division of Pharmacology, Nanjing, China
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37
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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Montessuit C, Lerch R. Regulation and dysregulation of glucose transport in cardiomyocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:848-56. [PMID: 22967513 DOI: 10.1016/j.bbamcr.2012.08.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 08/08/2012] [Accepted: 08/10/2012] [Indexed: 11/29/2022]
Abstract
The ability of the heart muscle to derive energy from a wide variety of substrates provides the myocardium with remarkable capacity to adapt to the ever-changing metabolic environment depending on factors including nutritional state and physical activity. There is increasing evidence that loss of metabolic flexibility of the myocardium contributes to cardiac dysfunction in disease conditions such as diabetes, ischemic heart disease and heart failure. At the level of glucose metabolism reduced metabolic adaptation in most cases is characterized by impaired stimulation of transarcolemmal glucose transport in the cardiomyocytes in response to insulin, referred to as insulin resistance, or to other stimuli such as energy deficiency. This review discusses cellular mechanisms involved in the regulation of glucose uptake in cardiomyocytes and their potential implication in impairment of stimulation of glucose transport under disease conditions. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.
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Affiliation(s)
- Christophe Montessuit
- Department of Medical Specialties, Geneva University Hospitals, Geneva, Switzerland.
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Abstract
GLUT4 is an insulin-regulated glucose transporter that is responsible for insulin-regulated glucose uptake into fat and muscle cells. In the absence of insulin, GLUT4 is mainly found in intracellular vesicles referred to as GLUT4 storage vesicles (GSVs). Here, we summarise evidence for the existence of these specific vesicles, how they are sequestered inside the cell and how they undergo exocytosis in the presence of insulin. In response to insulin stimulation, GSVs fuse with the plasma membrane in a rapid burst and in the continued presence of insulin GLUT4 molecules are internalised and recycled back to the plasma membrane in vesicles that are distinct from GSVs and probably of endosomal origin. In this Commentary we discuss evidence that this delivery process is tightly regulated and involves numerous molecules. Key components include the actin cytoskeleton, myosin motors, several Rab GTPases, the exocyst, SNARE proteins and SNARE regulators. Each step in this process is carefully orchestrated in a sequential and coupled manner and we are beginning to dissect key nodes within this network that determine vesicle-membrane fusion in response to insulin. This regulatory process clearly involves the Ser/Thr kinase AKT and the exquisite manner in which this single metabolic process is regulated makes it a likely target for lesions that might contribute to metabolic disease.
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Affiliation(s)
- Jacqueline Stöckli
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia
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Abstract
Despite daily fasting and feeding, plasma glucose levels are normally maintained within a narrow range owing to the hormones insulin and glucagon. Insulin increases glucose uptake into fat and muscle cells through the regulated trafficking of vesicles that contain glucose transporter type 4 (GLUT4). New insights into insulin signalling reveal that phosphorylation events initiated by the insulin receptor regulate key GLUT4 trafficking proteins, including small GTPases, tethering complexes and the vesicle fusion machinery. These proteins, in turn, control GLUT4 movement through the endosomal system, formation and retention of specialized GLUT4 storage vesicles and targeted exocytosis of these vesicles. Understanding these processes may help to explain the development of insulin resistance in type 2 diabetes and provide new potential therapeutic targets.
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